IP Routing on Cisco IOS, IOS Xe, and IOS Xr: An Essential Guide to Understanding and Implementing IP Routing Protocols

Route 99 Floating Static Routing 103 Recursive Lookup 105 Multihop Routing 108 Single Recursive Lookup 108 Multiple Recursive Lookups 109 Problems with Static Route Recursion 112 Null Interface 116 Static VRF Routes 121 References in This Chapter 124 Chapter 5 EIGRP 125 EIGRP Fundamentals 125 EIGRP Neighbors 126 Inter-Router Communication 126 Forming EIGRP Neighbors 128 Classic EIGRP Autonomous System Configuration 131 IOS network Statement 132 IOS XR 134 Passive Interfaces 134 Sample Topology and Configuration 134 Confirmation of Interfaces 136 Verification of EIGRP Neighbor Adjacencies 139 Display of Installed EIGRP Routes 140 Router ID 141 EIGRP Terminology 142 Topology Table 143 Path Metric Calculation 145 Custom K Values 148 Interface Delay Settings 149 Load Balancing 151 EIGRP Wide Metrics 153 Failure Detection and Timers 155 Convergence 156 Stuck in Active 159 Stub 160 Design Considerations with EIGRP Stubs 164 Summarization 166 Interface-Specific Summarization 166 Summarization Metrics 171 Advertising a Default Route 172 Automatic Summarization 172 Authentication 174 Enabling Authentication on the interface 174 Key Chain Configuration 174 WAN Considerations 177 IP Bandwidth Percent 177 Split Horizon 179 Next-Hop Self 182 EIGRP Named Configuration 184 Address Family Instance Configuration 185 Address Family Interface Configuration 186 Address Family Topology Configuration 188 Summary 189 References in This Chapter 189 Chapter 6 OSPF 191 OSPF Fundamentals 191 Inter-Router Communication 193 OSPF Hello Packets 194 Router ID 195 Neighbors 196 Forming OSPF Neighbor Adjacencies 197 Basic OSPF Configuration 202 IOS network Statement 202 IOS Interface Specific 204 IOS XR 205 Passive Interfaces 205 Sample Topology and Configuration 206 Confirmation of Interfaces 208 Verification of OSPF Neighbor Adjacencies 209 Verification of OSPF Routes 211 Designated Router and Backup Designated Router 212 Designated Router Elections 214 DR and BDR Placement 216 Failure Detection 219 Hello Timer 219 Dead Interval Timer 219 Verifying OSPF Timers 220 OSPF Fast Packet Hellos 220 OSPF Network Types 221 Broadcast 221 Non-Broadcast 222 Point-to-Point Networks 224 Point-to-Multipoint Networks 225 Loopback Networks 229 Review of OSPF Network Types 231 OSPF Adjacency with Different OSPF Network Types 231 Link Costs 235 Authentication 236 IOS Support for OSPF Authentication 236 IOS XR Support for OSPF Authentication 236 Summary 239 References in This Chapter 240 Chapter 7 Advanced OSPF 241 Areas 241 Area ID 245 OSPF Route Types 246 External OSPF Routes 247 Link-State Announcements 249 LSA Age and Flooding 251 LSA Types 251 LSA Type 1: Router Link 252 LSA Type 2: Network Link 257 LSA Type 3: Summary Link 259 LSA Type 5: External Routes 263 LSA Type 4: ASBR Summary 265 LSA Type 7: NSSA External Summary 268 LSA Type Summary 270 OSPF Path Selection 270 Intra-Area Routes 271 Interarea Routes 272 External Route Selection 272 E1 and N1 External Routes 273 E2 and N2 External Routes 273 Equal Cost Multi-Path 274 Summarization of Routes 274 Interarea Summarization 276 External Summarization 280 Default Route 283 OSPF Stubby Areas 286 Stub Areas 286 Totally Stubby Areas 289 Not-So-Stubby Areas 292 Totally NSSA Areas 295 Virtual Links 298 Discontiguous Network 301 Multi-Area Adjacency 304 Prefix Suppression 308 Summary 313 References in This Chapter 314 Chapter 8 IS-IS 315 IS-IS Fundamentals 315 Areas 318 OSI Addressing 319 Inter-Domain Part 320 Domain Specific Part 321 NET Addressing 322 Inter-Router Communication 323 IS Protocol Header 325 TLVs 326 IS PDU Addressing 326 Hello Packets 327 Link-State Packets 329 LSP Lifetime 329 LSP ID 330 LSP Sequence 331 Attribute Fields 331 LSP Packet and TLVs 332 IS-IS Neighbor 333 Ethernet 333 Point-to-Point 338 Basic IS-IS Configuration 340 IOS 340 IOS XR 340 Sample Topology and Configuration 341 Confirmation of IS-IS Interfaces 343 Verification of IS-IS Neighbor Adjacencies 346 Verification of IS-IS Routes 347 Designated Intermediate System 348 DIS Elections 351 DIS Placement 352 Point-to-Point Adjacency on Broadcast Media 353 Link State Packet Database 355 Viewing the LSPDB 356 Non-Pseudonode LSPs 357 Pseudonode LSPs 358 Building the Topology 359 Viewing the Topology 360 SPF Calculations 361 Passive Interfaces 362 Removal of Hello Padding 364 Failure Detection 366 Hello Timer 366 Hello Multiplier and Holding Timer 367 Authentication 367 IS-IS Hello Authentication 367 IS-IS LSP Authentication 368 Summary 371 References in This Chapter 372 Chapter 9 Advanced IS-IS 373 Advanced IS-IS Routing 373 Route Leaking 377 Backbone Continuity 380 Loop Prevention 382 Router-Specific IS-IS Levels 384 Interface Specific IS-IS Levels 385 Path Selection 386 Equal Cost Multi-Path 387 Interface Metrics 387 Overload Bit 394 Summarization 396 Default Routes 400 Prefix Suppression 401 Summary 405 References in This Chapter 406 Chapter 10 Border Gateway Protocol (BGP) 407 BGP Fundamentals 408 Autonomous System Numbers 408 Path Attributes 409 Loop Prevention 409 Address Families 410 Inter-Router Communication 410 Open Messages 412 Hold Time 412 BGP Identifier 413 Keepalive Messages 413 Update Messages 413 Notification Messages 414 BGP Sessions 415 BGP Neighbor States 415 Idle State 415 Connect State 415 Active State 416 OpenSent State 416 OpenConfirm State 417 Established State 417 Basic BGP Configuration 418 IOS 419 IOS XR 420 Verification of BGP Sessions 421 Prefix Advertisement 425 Receiving and Viewing Routes 427 iBGP 431 iBGP Full-Mesh Requirement 432 Peering via Loopback Addresses 433 eBGP 438 eBGP and iBGP Topologies 442 Next-Hop Manipulation 444 iBGP Scalability 446 Route Reflectors 446 Loop Prevention in Route Reflectors 451 Out-of-Band Route Reflectors 453 Confederations 453 Failure Detection 459 Security 459 eBGP Multihop 459 TTL Security 461 Summary 463 References in This Chapter 465 Part III Advanced Routing Techniques Chapter 11 Route Maps and Route Policy 467 Access Control Lists 467 Standard ACLs 468 Extended ACLs 469 IGP Network Selection 469 BGP Network Selection 470 Prefix Matching 471 Prefix Lists 473 Prefix Sets 474 Regular Expressions 475 _ (Underscore) 477 ^ (Caret) 478 $ (Dollar Sign) 478 [ ] (Brackets) 479 - (Hyphen) 479 [^] (Caret in Brackets) 480 ( ) (Parentheses and | Pipe) 480 . (Period) 481 + (Plus Sign) 481 ? (Question Mark) 481 * (Asterisk) 482 Looking Glass and Route Servers 483 AS_Path Access List 484 IOS XR AS_Path Selection Options 484 is-local 485 length 485 unique-length 486 passes-through 486 neighbor-is 487 originates-from 487 AS Path Set 488 Route Maps 488 Conditional Matching 490 Multiple Conditional Match Conditions 491 Complex Matching 491 Optional Actions 492 Continue 493 Route Map Examples 494 Routing Policy Language 496 Route Policy Structure 496 Match Statements 497 Attribute Modification 498 Common Route Policy Structure 499 Boolean Operators 504 Negation 504 Conjunction 504 Disjunction 505 Order of Processing 505 Comparing Prefix Sets to Prefix Lists 506 Parameterization 507 Route Policy Nesting 510 Original Value 511 Editors 512 RPL Examples 513 RPL Verification 515 Redistribution RPL Verification 516 BGP RPL Verification 517 References in This Chapter 519 Chapter 12 Advanced Route Manipulation 521 Conditional Routing of Packets 521 Policy-Based Routing Configuration 522 Access-List-Based Forwarding Configuration 523 Local PBR 525 Administrative Distance 526 Modifying EIGRP AD 528 Modifying OSPF AD 529 Modifying IS-IS AD 531 Modifying BGP AD 532 Route Filtering and Manipulation 534 EIGRP Filtering by Prefix 534 EIGRP Filtering by Hop Count 538 EIGRP Offset Lists 538 OSPF Filtering (Local) 541 OSPF Filtering (Area) 543 IS-IS Filtering (Local) 546 BGP Filtering 546 Clearing BGP Connections 549 Summary 550 References in This Chapter 550 Chapter 13 Route Redistribution 551 Redistribution Basics 553 Redistribution Is Not Transitive 553 Sequential Protocol Redistribution 555 Routes Must Exist in the RIB 555 Metrics 558 Protocol-Specific Configuration 558 Source-Specific Behaviors 560 Connected Networks 561 IS-IS 561 BGP 562 Destination-Specific Behaviors 563 EIGRP 563 OSPF 568 IS-IS 576 BGP 580 Challenges with Redistribution 582 Route Feedback 583 Suboptimal Routing 584 Invalid Routing Tables 589 Routing Loops 590 Methods to Avoid Routing Loops 593 Prefix Filtering 593 Tagging 595 Increase Seed Metrics 598 Administrative Distance 601 Summarization on Redistributing Router 603 Solutions to Redistribution Challenges 606 Summary 606 References in This Chapter 607 Part IV Advanced BGP Chapter 14 Advanced BGP 609 BGP Communities 609 Enabling BGP Community Support 610 Well-Known Communities 611 Internet 611 No_Export 611 No_Advertise 614 No_Export_SubConfed 617 Conditionally Matching BGP Communities 620 Community Set 621 Inline 622 Setting Private BGP Communities 625 Route Summarization 628 Aggregate Address 629 Flexible Route Suppression 632 Selective Prefix Suppression 632 Leaking Suppressed Routes 634 Atomic Aggregate 637 Route Aggregation with AS_SET 639 Route Aggregation with Selective Advertisement of AS_Set 641 Default Route Advertisement 643 Default Route Advertisement Per Neighbor 644 Conditional Route Advertisement 645 Outbound Route Filtering 647 Backdoor Networks 649 Maximum Autonomous System 652 Maximum Prefix 654 Remove Private Autonomous System 656 Allow Autonomous System 658 Local Autonomous System 660 Configuration Scalability 664 IOS Peer Groups 664 IOS Peer Templates 665 IOS XR Configuration Templates 667 Summary 668 References in This Chapter 669 Chapter 15 BGP Best Path Selection 671 BGP Best Path Overview 672 Weight 673 Local Preference 679 Locally Originated via Network or Aggregate Advertisement 684 Accumulated Interior Gateway Protocol 686 Shortest AS_Path 694 Origin Type 700 Multi-Exit Discriminator 704 Missing MED behavior 709 Always Compare Med 711 BGP Deterministic MED 713 eBGP over iBGP 714 Lowest IGP Metric 718 Prefer the Oldest EBGP Path 720 Router ID 720 Minimum Cluster List Length 721 Lowest Neighbor Address 722 BGP ECMP 723 eBGP and iBGP Multipath 723 eiBGP Multipath 726 R1 729 R2 730 XR3 730 XR4 730 XR5 731 AS_Path Relax 731 Suboptimal Routing with Route Reflectors 733 Additional Route Reflector 734 Shadow Route Reflector 735 Shadow Session Route Reflector 738 BGP Add-Path 739 Summary 742 Further Reading 743 Part V Multicast Chapter 16 IPv4 Multicast Routing 745 Multicast Fundamentals 745 Multicast Addressing 749 Layer 2 Multicast Addresses 752 Internet Group Management Protocol 753 IGMP Snooping 753 IGMPv2 756 IGMPv3 759 Multicast Distribution Trees 759 Source Trees 759 Shared Trees 760 Protocol Independent Multicast 762 PIM Dense Mode 765 PIM Sparse Mode 768 PIM Shared and Source Path Trees 768 Shared Tree Join 769 Source Registration 769 PIM SPT Switchover 771 Designated Routers 772 Rendezvous Points 772 Static RP 773 Auto-RP 773 Candidate RPs 773 RP Mapping Agents 774 PIM Bootstrap Router 775 Candidate RPs 775 Reverse Path Forwarding 776 PIM Forwarder 778 Basic Multicast Configuration 780 Configure Rendezvous Points 783 Static RP 784 Auto-RP 785 BSR 786 Multicast Verification 787 Bidirectional PIM 802 Bidir-PIM Designated Forwarder 804 Summary 808 References in This Chapter 809 Chapter 17 Advanced IPv4 Multicast Routing 811 Interdomain Multicast Routing 811 Multiprotocol BGP 812 Multicast Source Discovery Protocol 817 MSDP Source Active Message Types 818 SA Messages 819 Keepalive Messages 819 MSDP Peers 822 MSDP Verification 828 MSDP Stub Networks 831 Rendezvous Point Redundancy 833 Auto-RP with Multiple RPs 835 Auto-RP Group Filtering 836 BSR with Multiple RPs 840 BSR Group Filtering 843 BSR RP Hash Algorithm 845 Static RP with Multiple RPs 846 Anycast RP 847 Source Specific Multicast 850 SSM Mapping 857 DNS SSM Mapping 857 Static SSM Mapping 860 Multicast Security 862 Auto-RP Scoping 862 Multicast Boundaries 863 Administratively Scoped Boundaries 863 Auto-RP Multicast Boundaries 865 BSR Multicast Boundaries 866 Auto-RP Cisco-RP-Announce Message Filtering 867 PIM-SM Source Registration Filtering 867 PIM-SM Accept RP 868 PIM Neighbor Control 869 PIM Register Rate Limit 870 Multicast Traffic Engineering 871 RPF Rules 871 Static Mroutes 872 MBGP 875 Static IGMP Joins 882 Multicast Troubleshooting 886 Mtrace 887 Summary 889 References in This Chapter 891 Part VI IPv6 Chapter 18 IPv6 Addressing 893 IPv6 Address Structure 893 Text Representation Address Abbreviation 895 IPv6 Hexadecimal to Binary Conversion 896 IPv6 Address Types 898 Unicast 898 Global Unicast 900 Unique Local Unicast 904 Link-Local Unicast 905 Anycast 906 Multicast 908 Special IPv6 Addresses 911 Neighbor Discovery Protocol 912 Router, Prefix, and Parameter Discovery. 913 Redirect 919 IPv6 Stateless Address Autoconfiguration 920 Extended Unique Identifier 920 SLAAC Router Configuration 921 RA Options for DNS 923 Stateless DHCPv6 924 IOS Stateless DHCPv6 Configuration 924 IOS XR Stateless DHCPv6 Configuration 925 Stateless DHCPv6 Verification 926 Stateful DHCPv6, Relay Agent, and Relay Proxy 926 IOS Relay Agent Configuration 927 IOS Relay Agent Verification 928 IOS XR Proxy Agent Configuration 928 IOS XR Proxy Agent Verification 929 IOS Stateful DHCPv6 Server Configuration 930 IOS XR Stateful DHCPv6 Server Configuration 931 Stateful DHCPv6 Server Verification 932 IPv6 Address Resolution and Neighbor Unreachability Detection 934 Duplicate Address Detection 937 Summary 938 References in This Chapter 939 Chapter 19 IPv6 Routing 941 Static Routing 941 Static Route Configuration 942 Static Route Reference Chart for IPv6 943 EIGRPv6 944 EIGRPv6 Inter-Router Communication 944 EIGRPv6 Configuration 945 IOS EIGRPv6 Autonomous System Configuration (Classic) 945 IOS EIGRPv6 Hierarchical Configuration (Named Mode) 946 IOS XR EIGRPv6 Configuration 946 EIGRPv6 Verification 947 Summarization 950 Default Route 952 Route Filtering 953 EIGRP Configuration Command Reference Chart for IPv6 954 OSPFv3 956 OSPFv3 Inter-Router Communication 957 OSPFv3 Link-State Advertisement 958 OSPFv3 LSA Flooding Scope 959 OSPFv3 Configuration 960 IOS OSPFv3 Configuration 960 IOS XR OSPFv3 Configuration 961 OSPFv3 Verification 962 OSPFv3 Authentication 970 OSPFv3 Multiple Instances 973 OSPFv3 Configuration Command Reference Chart for IPv6 975 Integrated IS-IS for IPv6 977 IS-IS Inter-Router Communication 978 IS-IS Type-Length-Value 978 IS-IS Topology Modes 978 IS-IS Configuration 979 IOS Base Configuration 979 IOS XR Base Configuration 980 IOS Topology Mode Configuration 981 IOS XR Topology Mode Configuration 981 Verification 985 IS-IS Configuration Reference Chart for IPv6 987 Multiprotocol BGP for IPv6 989 Inter-Router Communication 989 BGP Configuration 991 IOS Base Configuration 991 IOS XR Base Configuration 992 BGP Verification 993 IPv6 over IPv4 BGP Sessions 998 BGP Configuration Command Reference Chart for IPv6 1001 IPv6 Route Redistribution 1002 Summary 1006 References in This Chapter 1006 Chapter 20 IPv6 Multicast Routing 1007 IPv6 Multicast Routing Overview 1007 IPv6 Multicast Address Mapping into MAC Address 1009 Enabling Multicast Routing 1010 Multicast Listener Discovery 1010 Protocol Independent Multicast 1015 PIM Sparse Mode 1015 Static RP 1017 Bootstrap Router 1018 Embedded RP 1021 IPv6 Multicast Verification Commands 1024 Reverse Path Forwarding 1030 Multicast Boundary Scope 1032 PIM Source Specific Multicast 1033 Summary 1034 References in This Chapter 1035 Index 1037 Part VII High Availability Chapter 21 High Availability Online Appendixes Appendix A Decimal to Hex to Binary Values Online Appendix B BGP Attributes Online

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